Heating unit manufacture



March 26, 1963 c. F. LOUTHAN 3,082,511

HEATING UNIT MANUFACTURE Filed Nov. 14. 1957 2 Sheets-Sheet 1 if u 94 a it 9' I II I 614 i F 3'4 a a9 I 59 v i .42 d gg E W I! HIS ATTORNEY March 26, 1963 c. F. LOUTHAN HEATING mm MANUFACTURE 2 Sheets-Sheet 2 Filed Nov. 14, 1957 INV EN TOR. C'Jefi'er [oz/291a HIS ATTORNEY 3,082,511 HEATING UNIT MANUFACTURE Chester F. Louthan, Dayton, Ohio, assignor to General Motors Corporation, Detroit, Mich a corporation of Delaware Filed Nov. 14, 1957, Ser. No. 696,414 3 Claims. (Cl. 29-15565) This invention relates to tubular sheath electric heating units that are commonly used as surface heaters for electric ranges and the like and more particularly to a method and apparatus formanufacturing these heating units.

An object of this invention is to provide a method and apparatus for manufacturing a tubular sheath heating element of the type having a tubular sheath containing one or more heating elements and a quantity of compacted finely divided electrical insulating material, and wherein the use of the method and apparatus of this invention results in a high degree of compacting of the finely divided material and also results in a finished product wherein the heating element or elements are spaced a predetermined distance from the tubular sheath along the entire length of the sheath and irrespective of the fact that the sheath may have been initially bowed. The foregoing object is preferably accomplished by supporting the tubular sheath in a vertical position and threading a heating element through the tubular sheath and through a tamping or spacer plug that is located within the tubular sheath and which has certain of its edges in contact with the internal walls of the tubular sheath. The tubular sheath is then supplied with a quantity of finely divided insulating material such as magnesium oxide and at the same time the tubular sheath is vibrated along the longitudinal vertical axis to cause vertical reciprocation of the spacer or tamping plug. At each reciprocation of the tamping plug a quantity of insulating material passes around the plug and is compacted by the downward stroke of the tamping plug. During this vertical reciprocation, the tamping plug climbs in increments from the bottom of the tubular sheath to the top thereof and highly compacts the finely divided insulating material during its movement. The tamping plug in its movement follows the contour of the tubular sheath and thus correctly spaces the electrical heating element from the tubular sheath, the spacing being the same over the entire length of the tubular sheath.

It is another object of this invention to provide an end connection for a plurality of heating element wires Wherein one end of one of the heating elements is folded over another to form a heating element cluster and wherein the cluster is forced into a tapered opening formed in a supporting plug, the heating elements being threaded through said opening except for the cluster which is tightly en' gaged by the walls of the tapered opening.

heating element;

FIGURE 4 is a sectional view taken along line 4-4 of FIGURE 1;

FIGURE 5 is a vertical sectional view of apparatus for 3,082,511 Patented Mar. 26, 1963 ice filling a tubular sheath heating element wherein the heating unit contains a plurality of heating elements;

FIGURE '6 is a sectional view taken along line 66 of FIGURE 5;

FIGURE 7 is a sectional view taken along line 7-.-7 of FIGURE 5;

FIGURE 8 shows one step of making an end connection having a plurality of heating elements; and

FIGURE 9 illustrates a second step of forming an end connection having a plurality of heating elements.

Referring now to the drawings and more particularly to FIGURE 1 the heating element filling machine of this invention comprises a main frame 10 that includes vertically extending side frame members 12 and 14. The side frame members 12 and 14 are connected by a cross member 16 which is bolted to the side frame and which has an opening 18 that is adapted to receive a metal tubular sheath 20 that forms a component part of a heating unit. The side frames 12 and 14 carry a plurality of reinforcing blocks 22 that are formed with vertically extending openings 24 that are aligned with openings 26 formed in the side frames. The openings 24 and 26 form guides for a vertically movable heating element supporting frame generally designated by reference numeral 28.

The vertically movable frame 28 includes a supporting block 30 which carries vertically extending parts 32 having studs 34 that are threaded into threaded openings in block 3t). The heating supporting frame 28 further includes a cross member 36 that is held in fixed relation to blocks 32 by means of screws 38 which may be tightened I to bear against blocks 32 and which provide an adjustable connection between the cross member 36 and blocks 32. The block 36 is provided with an opening 40 that is adapted to receive a supporting rod 42 and also has a set screw 43 that engages the rod 42 to hold it in fixed relationship with the cross member 36. The cross member 36 carries rods 44 that fit within the slots 24 and 26. The block 30 carries similar rods 46 that slide Within vertical openings 24 and 26. The rods 44 and 46 are thus contained within slots 24 and 26 and this arrangement prevents the frame 28 from rotating during vertical reciprocation thereof.

The filling machine of this invention has an impact vibrator 47 that may be either air operated or electrically operated and which operates to vertically reciprocate a block 48 having a recess 49. The block 48 is prevented from rotating by a guide 50 that is suitably attached to side frame 14. A similar block (not shown) may be disposed on the opposite side of vibrating block 48 in order to prevent the block 43 from rotating during its vibratory reciprocating movement. The vibrator 47 is preferably mounted in fixed relationship to the main frame of the machine by means (not shown). Where the frame is floor mounted the vibrating mechanism 47 may also be floor mounted, and as noted above, the vibrator 47 may be air operated and may take the form of an air-hammer.

When it is desired to fill a tubular sheath heating unit a tubular metal member 20 is fitted with a wire coil heating or resistance element 52 that is welded or other- -wise secured to metal rod terminals 53 and 54. In setting up the machine for a filling operation a metal thimble 55 is threaded over'the heating element and terminal 54 to a point where the thimble engages projections 56 for-med integrally with the terminal 54. The thim-ble has a central opening as illustrated in FIGURE 1 through which the heating element 52 and terminal 54 are threaded. The heating element 52 is also threaded through a freely mounted tubular tamping rod 57 that has a lower cross section better shown in FIGURE 4. The lower end of the tubular tamping rod is formed with flat edges 58 and with arcuate edges 59 that contact the tubular metal sheath 20. The edges 59 are in point contact with the inner wall of tubular sheath 20 .to keep the tamping rod 57 centralized within the tubular sheath 20 during vertical reciprocation thereof.

The upper terminal 53 is held in fixed engagement with the lower endof rod 42 by providing a reduced portion 60 on the rod 53 which fits Within a slot 61 formed in the supporting rod 42. The terminal 53 is detachably connected to the lower end of rod 4 2 by simply slipping the end of terminal 53 into the openings formed in the rod 42 with the large diameter portion 63 of the terminal fitting over the annular portion 64- of rod 42. This connection between rod 42 and terminal 53 may be made after threading the heating element 52 through the tamping rod 57, and when the supporting rod 42 and heating element 52 are threaded therethrough the rod may be fixed in place by the set. screw 43.

When the tamping rod 57 and heating element 52 have been threaded through the tubular sheath 20 the sheath is positioned in the machine and the set screw 65 is tightened to hold the tubular sheath 20 in fixed relationship with cross member 30. In this position the lower end of tubular sheath 20 rests on the lower wall of recess 49 and a process fitting generally designated by reference numeral 66 and shown in detail in FIGURE 2 may then be attachedto the tubular sheath 20. The process fitting as shown in FIGURE 2 includes blocks 67 and 68 having arcuate recesses that are adapted to engage the outer periphery of tube '29. The blocks 67 and 68 are held together by threaded fasteners 69 which may be loosened or completely unthreaded to remove the process fitting from the position shown in FIGURE 1. The process fitting in its position in the machine lies directly on the vertically vibrating member 48 and the vertical reciprocation of the vibrating member 48 is transferred to the tube 20 through the process fitting 66.

The cross member 30 carries a hopper 70 having a conduit portion 71 of predetermined cross sectional area. The hopper is adapted to contain a quantity of finely divided insulating material such as magnesium oxide. The insulating material is fed through chute 71 into an opening 72 formed in block 30 which communicates with the space between tamping rod 57 and tubular sheath 20. The chute 71 may be provided with any suitable valve mechanism for controlling the flow of magnesium oxide into the tubular sheath 2!) and may be designed to feed any desired quantity of magnesium oxide into tubular sheath 20 for a predetermined or given period of time.

A weight member 73 is secured to the upper end of tamping rod 57 by means of a set screw as shown in FIGURE 1. The weight member 73 slidably engages one side of a guide member 73a that is fixed to frame 28, thus preventing rotation of the tamping rod 51 during reciprocation thereof. This weight provides for extra downward force when the tamping rod 57 is being vertically reciprocated. A spring 74 is interposed between cross member 16 and process fitting 66 and the force of this spring operates to move the process fitting 66 downwardly during vertical reciprocation thereof.

When the machine has been set up in the manner illustrated in FIGURE 1, the vibrator 47 is operated to vertically reciprocate the block member 48, the sheath 20 and frame 28 which carries sheath 20. During this vertical reciprocation the tamping rod '57 is vertically reciprocated within the tubular sheath 2t and simultaneously with this vertical reciprocation magnesium oxide is fed between the tamping rod 57 and the tubular sheath 20*. The magnesium oxide powder passes between the edges '58 of tamping rod 57 and the tubular sheath 20, and starts to fill up the tube 20. This magnesium oxide is designated by reference numeral 75 in FIGURE 1. The vertical reciprocation of tamping rod 57 causes the mag nesium oxide to flow thereby, and on each downward stroke compacts the quantity of magnesium oxide located below the tamping rod. The tamping rod during this vertical reciprocation moves upwardly within the tubular sheath 20, the tamping rod climbing slightly upwardly during each singular vertical reciprocation. Since the vibrator 47 is operated relatively rapidly the tamping rod climbs up within tubular sheath 20 in small increments as long as the vibrator 47 is in operation. The tamping rod 57 will thus move from the lower end of tubular sheath 20 to the top end thereof and when the tamping rod reaches the top end the tubular sheath 20 will be completely filled with compacted magnesium oxide.

It is to be noted that the tamping rod serves another function in that it spaces the heating element 52 away from the inner wall of tubular sheath 20' during its up ward vibratory movement. The tamping rod due to the engagement of edges 59 with the tubular sheath 20 follows the contour of the tubular sheath 20 and thus insures that the heating element 52 will be spaced 2. predetermined distance from the tubular sheath '20 regardless of the fact that the tube 20 might be slightly bowed. It is also to be noted that the heating element 52 is neither tensioned nor slackened during the vibratory movement of the tamping rod due to the fact that the upper end of the heating element is fixed to movable frame 28 whereas the lower end is fixed to the tube '20. Thus during vertical reciprocation of the tube 20, and tamping rod 57, a predetermined fixed spacing is provided between the ends of the heating element 52 to insure that it is neither tensioned nor slackened.

The apparatus shown in FIGURE 1 may also be used to till a tubular sheath heating unit of the typeillustrated in FIGURE 5 wherein the finished product contains three heating elements that are spaced from one another by predetermined distances. In the embodiment shown in FIGURE 5 a metal tube 76 has a circular cross section except for a portion 77 that is flattened. In the embodiment of FIGURE 5, a plug 78 is provided which has a tapered opening 80 that is of smaller diameter adjacent its top end thereof. The plug 78 has a shoulder 82 which is adapted to engage one end of the flattened portion 77 of the tube 76 when the plug is inserted therein. The plug is preferably formed of crushable ceramic material and is adapted to support wire coil heating or resistance elements 83 and 84 in a manner illustrated in FIGURE 5.

In order to assemble the heating elements 83 and 84 within the plug 78 the heating elements are threaded through the plug 78 in a manner illustrated in FIGURE 8 wherein the heating element 83 is formed with a looped end 85 and wherein the heating element 84 is threaded through plug 78 and passed over the looped end 85 of heating element 83. With the heating elements in the position shown in FIGURE 8 the end of heating element 84 is bent over the looped end of heating element 83 in a manner depicted in FIGURE 9. In this position of the heating elements 83 and 84 a heating element cluster isformed which is pulled into the tapered opening 89 and which tightly engages the side walls of the opening 80. It has been found that by forming the bunch or cluster as illustrated in FIGURE 9 a tight connection may be made with plug 78 which supports the lower end of the heating elements within the tubular sheath 76.

When the heating elements 83- and 84 have been secured to the plug 78 in a manner shown in FIGURES 8 and 9, and when the heating elements 83 and 84 have been positioned in the plug 78, the three terminal ends 86, 87 and 88 of the two heating elements are threaded through openings 86a, 87a, and 88a formed in a tamping plug or spacer plug 89. The plug 89 has a flat side 90 that is adapted to cooperate with the fiat side 77 of tubular sheath 76 to prevent rotation of plug 89 during vertical reciprocation thereof. The plug 89 is attached to a rod 91 which in turn carries a weight 92 that is fixed to the rod by means of a set screw 93. The terminal ends 86, 87 and 88 of the heating elements are connected with terminals 93 which fit within openings 9 formed in a fitting 95 that is carried by the upper end of tubular sheath 76. The fitting has set screws 96 which engage the terminals 93 to hold the terminals in fixed relationship with the tubular sheath 76. The fitting 95 has an opening that accommodates the rod 91 and has openings 99 which permit the passage of magnesium oxide therethrough during vertical reciprocation of the tamping plug 89. A filler chute member 97 may also be fitted to the fitting 95 in a manner shown in FIGURE 5 to provide for guiding means for the magnesium oxide insulating material.

As noted hereinbefore the machine shown in FIGURE 1 is useful in filling tubular sheath heating units of the type illustrated in FIGURE 5. In filling the unit of FiGURE 5 the tubular sheath 76 is secured to the process fitting 66 shown in FIGURE 1, and the upper end of the tubular sheath 7 6 is fixed to the cross member 30 in a manner similar to the securing of tubular sheath to cross member and process fitting 66. The chute 71 is disposed to overlie the chute 97 whereby the hopper 70 is adapted to feed magnesium oxide into the chute 97. When the tube 76 of FIGURE 5 is inserted within the machine shown in FIGURE 1, the tube 76 is vibrated along its longitudinal axis to produce a longitudinal vibration of tamping plug 89, rod 91 and Weight 92. The tamping plug 89 and its associated parts climb upwardly within the tubular sheath 76 in a manner similar to the climbing up of tamping rod 57 Within tubular sheath 20. In the apparatus of FIGURE 5 the three heating elements 86, 87 and 88 are held at predetermined distances from one another and from the tubular sheath 76 due to the fact that they are threaded through the openings in spacer or tamping plug 89. 'The magnesium oxide represented by reference numeral 98 is compacted during the vertical reciprocation of tamping plug 89 to form a highly compacted mass within tubular sheath 76. It will be apparent that the operation of the apparatus shown in FIGURE 5 and in FIGURE 1 is substantially identical the difference being that three heating elements are being positioned Within the tubular sheath in FIG- URE 5 whereas in FIGURE 1 only a single heating element is being fitted within the tubular sheath.

When the tamping rod 89 has moved from the lower end of tubular sheath 76 to the top end thereof, the tube is completely filled and an end cap (not shown) may then be attached to the lower end thereof. The tube is then removed from the machine and may be swaged to crush the crushable member 78, the material of member 78 being thus highly compacted to hold the ends of heating elements 86, 87 and 88 together and from moving along the length of tubular sheath 76.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted as may come within the scope of the claims which follow.

What is claimed is as follows:

1. The method of manufacturing a heating unit of the type having a tubular metal sheath containing a heating element and a packing of insulating material comprising the steps of, supporting said metal tubular sheath in a vertical position, supporting said heating element within said tubular sheath, freely mounting a continuously unsupported tubular tamper member within said metal tubular sheath with said heating element being threaded through said tamper member, closing the bottom end of said tubular metal sheath, securing said heating element at the bottom end of said tubular sheath to correctly position said heating element within said tubular sheath,

supplying the space between said tubular sheath and said tubular tamper member with granular insulating material, and directly vertically reciprocating said tubular sheath axially in a manner to cause said unsupported tubular tamper member to move upwardly a greater distance per reciprocating stroke than said sheath thereby to leave a space between said tamper member and the previously compacted surface of the insulating material into which space the granular material can flow and cause the tamper member to rise in said sheath with each reciprocating movement.

2. The method of manufacturing a heating unit of the type having a tubular metal sheath containing a heating element and a packing of insulating material comprising the steps of, supporting said tubular sheath in a vertical position, continuously freely mounting a tamping plug having a vertically disposed opening in said tubular sheath, supporting a heating. element in said tubular sheath within the tamping plug, closing the bottom end of said tubular metal sheath, securing said heating element to said bottom end to correctly position said heating element Within said tubular sheath, feeding granular insulating material into said tubular sheath, and directly vertically reciprocating said tubular sheath along its longitudinal axis in a manner to cause said tamping plug to reciprocate vertically upwardly in said tubular sheath a greater distance than said tubular sheath and solely in response to the reciprocations of said tubular sheath whereby to form a space between said tamping plug and the previously compacted surface of the insulating material into which space the granular material can flow for eifecting the rise of said tamping plug in said tubular sheath with each reciprocation.

3. The method of manufacturing a heating unit of the type having a tubular metal sheath containing a heating element and a packing of insulating material comprising the steps of, supporting said tubular sheath in a vertical position, continuously freely mounting an unsupported tamping plug in said tubular sheath, supporting a heating element in said tubular sheath adjacent the tamping plug, closing the bottom end of said tubular sheath, fixing said heating element relative to said bottom end, directly vertically reciprocating said tubular sheath along its longitudinal axis in a manner to cause said tamping plug to move upwardly a greater distance per reciprocating stroke than said sheath thereby to leave a space between said tamping plug and said bottom end, and feeding granular insulating material into said space whereby to cause said tamping member to move incrementally upwardly in said sheath while said granular material is being compacted between said bottom end and said tamping plug.

References Cited in the file of this patent UNITED STATES PATENTS 1,359,400 Lightfoot Nov. 16, 1920 1,474,723 Levinson Nov. 20, 1923 1,547,335 Lightfoot et al. July 28, 1925 1,588,558 Thornton June 15, 1926 1,669,385 Wiegand et al. May 8, 1928 2,311,358 Baily :Feb. 16, 1943 2,469,801 Vogel et al. May 10, 1949 2,472,145 Cappell June 7, 1949 2,477,226 Ashton July 26, 1949 2,591,925 Erbe Apr. 8, 1952 2,652,622 Charbonneau Sept. 2-2, 1953 FOREIGN PATENTS 105,716 Australia Nov. 17, 1938 932,471 France Mar. 23, 1948 1,131,200 France Feb. 18, 1957 528,718 Great Britain Nov. 5, 1940 

3. THE METHOD OF MANUFACTURING A HEATING UNIT OF THE TYPE HAVING A TUBULAR METAL SHEATH CONTAINING A HEATING ELEMENT AND A PACKING OF INSULATING MATERIAL COMPRISING THE STEPS OF, SUPPORTING SAID TUBULAR SHEATH IN A VERTICAL POSITION, CONTINUOUSLY FREELY MOUNTING AN UNSUPPORTED TAMPING PLUG IN SAID TUBULAR SHEATH, SUPPORTING A HEATING ELEMENT IN SAID TUBULAR SHEATH ADJACENT THE TAMPING PLUG, CLOSING THE BOTTOM END OF SAID TUBULAR SHEATH, FIXING SAID HEATING ELEMENT RELATIVE TO SAID BOTTOM END, DIRECTLY VERTICALLY RECIPROCATING SAID TUBULAR SHEATH ALONG ITS LONGITUDINAL AXIS IN A MANNER TO CAUSE SAID TAMPING PLUG TO MOVE UPWARDLY A GREATER DISTANCE PER RECIPROCATING STROKE THAN SAID SHEATH THEREBY TO LEAVE A SPACE BETWEEN SAID TAMPING PLUG AND SAID BOTTOM END, AND FEEDING GRANULAR INSULATING MATERIAL INTO SAID SPACE WHEREBY TO CAUSE SAID TAMPING MEMBER TO MOVE INCREMENTALLY UPWARDLY IN SAID SHEATH WHILE SAID GRANULAR MATERIAL IS BEING COMPACTED BETWEEN SAID BOTTOM END AND SAID TAMPING PLUG. 